Bicyclist Head Injuries in Victoria Three Years after the Introduction of Mandatory Helmet Use

Executive Summary

The mandatory bicycle helmet wearing law implemented in Victoria on 1 July, 1990 was
successful in building on past efforts to promote helmet use by bringing helmet wearing
rates to new high levels for all cyclist age groups in the first post-law year, both in
Melbourne and Victoria as a whole. Estimates of trends in helmet wearing over all three
post-law years were, however, not available for this report.

The continuing influence of bicycle helmet wearing on bicyclist head injuries three
years after the introduction of mandatory wearing is evaluated here by building on the
results of the two previous evaluations of the bicycle helmet wearing law conducted by the
Monash University Accident Research Centre (Cameron et al 1992, Finch et al 1993b).
Results are presented for both metropolitan Melbourne and the whole of Victoria and the
study uses data sourced from motor vehicle involved bicyclist injury claims from the
Transport Accident Commission (TAC) as well as Victorian hospital admissions records of
injured cyclists.

Analysis of hospital admissions records using logistic regression was not able to find
a relationship between helmet wearing and head injury rates in the immediate pre-law years
for bicyclists injured in accidents not involving a motor vehicle. Despite this, head
injury rates for bicyclists injured in these crashes was significantly lower than the
pre-law level in each of the three post-law years. A significant inverse relationship
between helmet wearing and head injury rate was found for cyclists involved in accidents
with motor vehicles. This relationship was found in analysis of both TAC insurance claims
data and hospital admissions records.

The effect of the bicycle helmet law in reducing head injury rates below pre-law trend
predictions for bicyclists injured in motor vehicle involved crashes was not clear.
Analysis of the TAC claims data showed bicyclist head injury rates significantly below
pre-law trend predictions in the second post-law year although this benefit appeared to
have been lost in the third post-law year, with an increase in head injury rate from the
second post-law year. Analysis of the hospital admission records however, failed to show
any additional benefit of the law over pre-law trends in reducing head injury rates in the
three post-law years (an increase in head injury rate in the third post-law year was also
observed here). Comparison of the TAC claims data and hospital admission records for
non-fatal motor vehicle involved bicyclist injuries revealed possible differences in
injury coding between the two.

A subsequent MUARC report (Carr et al 1995), which should be read in conjunction with
this report, investigates bicycle injury data and the effect of the bicycle helmet law
four years after its introduction. This report has revealed biases in the bicyclist injury
data, certainly affecting the analysis and results presented here. This is shown by the
analysis of Carr et al (1995) which adjusts for the bias in the bicyclist injury data and
reaches different conclusions to those drawn here.

Sponsoring Organisation: Baseline Research Program - Department of Justice,
Transport Accident Commission, Royal Automobile Club of Victoria (RACV) Ltd,
VicRoads